Linked Life Data

1918057

Source:http://linkedlifedata.com/resource/pubmed/id/1918057

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
29
pubmed:dateCreated
1991-11-14
pubmed:databankReference
pubmed:abstractText
We have characterized a maltodextrin glucosidase, previously described as a maltose-inducible, cytoplasmic enzyme that cleaves p-nitrophenyl-alpha-maltoside in Escherichia coli. The gene encoding the enzyme activity, referred to as malZ, is located at 9.3 min on the chromosomal map. We cloned the gene in a high copy number vector and purified the enzyme. It is a monomer, with an apparent molecular weight of 65,000. The enzyme degrades maltodextrins, ranging from maltotriose to maltoheptaose, to shorter oligosaccharides, the final hydrolysis products being maltose and glucose. We measured the kinetic parameters, Km and Vmax, for the hydrolysis to glucose of the five different substrates. The binding of the substrate is enhanced by increasing the number of glucosyl residues in the maltodextrin. In contrast, the maximum rate of hydrolysis (Vmax) is fastest for maltotriose. To study the mode of action of the enzyme, we quantitatively measured the amount of free glucose liberated from the different maltodextrin substrates after a long incubation. More glucose is liberated from the long dextrins, as compared to the shorter ones, showing that the primary hydrolysis product was glucose, not maltose. Furthermore, [14C]maltotriose, specifically labeled at the reducing end, was hydrolyzed to [14C]glucose and unlabeled maltose. These data demonstrate that the malZ gene product is a maltodextrin glucosidase, liberating glucose from the reducing end of malto-oligosaccharides. The nucleotide sequence of malZ and the deduced amino acid sequence showed that malZ encodes a protein with a molecular weight of 68,960. Homology to glucosidases, alpha-amylases, and pullulanases were observed. Conserved regions thought to represent active sites in dextrin hydrolases were found in the MalZ protein.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
266
pubmed:geneSymbol
malZ
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
19450-8
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
The malZ gene of Escherichia coli, a member of the maltose regulon, encodes a maltodextrin glucosidase.
pubmed:affiliation
Department of Biology, University of Konstanz, Federal Republic of Germany.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't